Radiation intensity of lignite-fired oxy-fuel flames |
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| Institution: | 1. Department of Energy Technology, Lappeenranta University of Technology, Lappeenranta, Finland;2. Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, Gliwice 44-101, Poland;1. Department of Energy and Environment, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden;2. Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden;3. Department of Energy Technology, SP Technical Research Institute of Sweden, Box 857, SE-501 15 Borås, Sweden;1. Energy Systems and Technology, Technische Universität Darmstadt, Otto-Berndt-Str. 2, 64287 Darmstadt, Germany;2. Measurement Science and Standards, National Research Council Canada, Ottawa, Ontario, Canada K1A 0R6;3. Aix-Marseille Université, IUSTI/ UMR CNRS 7343, 5 rue E. Fermi, 13453 Marseille Cedex 13, France;1. Energy 2050, Department of Mechanical Engineering, University of Sheffield, Sheffield S10 2TN, UK;2. State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China |
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| Abstract: | The radiative heat transfer in oxy-fuel flames is compared to corresponding conditions in air-fuel flames during combustion of lignite in the Chalmers 100 kW oxy-fuel test facility. In the oxy-fuel cases the flue-gas recycle rate was varied, so that, in principle, the same stoichiometry was kept in all cases, whereas the oxygen fraction in the recycled flue-gas mixture ranged from 25 to 29 vol.%. Radial profiles of gas concentration, temperature and total radiation intensity were measured in the furnace. The temperature, and thereby the total radiation intensity of the oxy-fuel flames, increases with decreasing flue-gas recycle rate. The ratio of gas and total radiation intensities increases under oxy-fuel conditions compared to air-firing. However, when radiation overlap between gas and particles is considered the ratios for air-firing and oxy-fuel conditions become more similar, since the gas-particle overlap is increased in the CO2-rich atmosphere. A large fraction of the radiation in these lignite flames is emitted by particles whose radiation was not significantly influenced by oxy-fuel operation. Therefore, an increment of gas radiation due to higher CO2 concentration is not evident because of the background of particle radiation, and, the total radiation intensities are similar during oxy-fuel and air-fuel operation as long as the temperature distributions are similar. |
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